The aim of this research is to define the relationships among physiological stimuli (odors), single unit and ensemble neural responses, and the circuitry of the peripheral olfactory pathway. These experiments seek to define the principles by which odor information is encoded, relayed, and integrated by the olfactory receptors and the synaptic circuits of the olfactory bulb. Several different methods will be used to assess how individual units, as well as how groups of elements function. The receptor responses will be examined using 2-deoxyglucose (2DG) mapping and voltage-sensitive dye recording (VSDR) after controlled odor presentation. Receptor properties will be correlated with bulbar responses observed using intracellular recording with HRP staining, 2DG mapping, and VSDR after controlled odor delivery. In this way, the encoding and manipulation of odor sensory information may be followed through receptor and bulbar elements. The salamander has been chosen as a model system because of its demonstrated anatomical, physiological, and behavioral advantages. It is anticipated that these studies will provide insight into mechanisms by which odors are encoded by the CNS, as well as insight on characteristics of information processing in local circuits. Since local circuitry, similar to that seen in the olfactory bulb, has been found in other brain regions, information gathered about synaptic mechanisms in the bulb may provide a view into the function of such circuits elsewhere. The olfactory pathway is one of the principle sensory inputs to several phylogenetically old brain regions, including pyriform cortex, olfactory tubercle, and amygdala. As such, analysis of the sense of smell may permit investigations of these complex regions which, in animals, relate to critical functions such as food recognition and mate selection and which, in humans, are thought to be involved in pathological states such as epilepsy and schizophrenia. One of the first steps in analyzing these higher relays is to investigate their inputs. It is for investigation of this initial stage of odor information processing that this proposal seeks support.